The present invention relates generally to railroad tank cars and more specifically to manway covers for railway cars.
Railroad tanks are used to transport a wide variety of different types of commodities. Tank cars must be designed to accommodate a variety of commodities that create high internal pressure within the tank.
Railroad tank cars typically have one or more manway access openings on their top surface which allow workers to climb into the tank car to inspect, repair or clean the interior thereof. The manways typically comprise a cylindrical tube that communicates with an access opening in the tank and a manway cover assembly that is positioned in sealing relationship to the manway nozzle.
Manway covers have heretofore typically been flat or outwardly convex in shape and have been provided with sealing gaskets to maintain the pressure within the tank when the cover is in its closed position. Examples of such manway covers are disclosed in U.S. Pat. No. 6,076,471.
However, such flat or outwardly convex manway covers are susceptible to failure at high internal pressures (i.e. psi), particularly when the manway cover is made of stainless steel.
Accordingly, there is a need for a manway cover design that can accommodate higher internal tank pressures whether made from either carbon steel or stainless steel or a combination thereof.